Transmission circuit for an electronic telephone set

Abstract

A transmission circuit for an electronic telephone set has a transmit circuit which as far as direct current is concerned is connected in parallel with the series arrangement of a logic circuit, a current source and a receive circuit. This enables the voltage space of the transmit circuit to be equal to the line voltage so that a maximum transmit level can be achieved.

What is claimed is: 
     
       1. A transmission circuit for an electronic telephone set comprising a receive circuit, a transmit circuit, and a logic circuit for generating tone signals; said logic circuit being in series arrangement with said transmit circuit for such tone signals and forming a series arrangement with said receive circuit for direct current; and for direct current said transmit circuit being connected in parallel with said direct current series arrangement of said logic circuit and said receive circuit. 
     
     
       2. The transmission circuit of claim 1 wherein said direct current series arrangement of said logic circuit and said receive circuit further comprises a current source connected in series between said logic circuit and said receive circuit for reducing the possibility of mutual interaction between said circuits for alternating current voltages. 
     
     
       3. The transmission circuit of claim 2 wherein said receive circuit comprises amplifier means having a transistor output circuit, an electro-acoustic transducer and a capacitor; said electro-acoustic transducer being parallel connected to said transducer output circuit through said capacitor.